Atomic force microscopy and near-field optical imaging of a spin transitionElectronic supplementary information (ESI) available: Far-field and near-field movies of the spin transition and SEM images of the NSOM tip. See DOI: 10.1039/c3nr03030j

We report on atomic force microscopy (AFM) and near-field scanning optical microscopy (NSOM) investigations of single crystals of the spin crossover complex {Fe(pyrazine)[Pt(CN) 4 ]} across the first-order thermal spin transition. We demonstrate for the first time that the change in spin state can be probed with sub-micrometer spatial resolution through various topographic features extracted from AFM data. This original approach based on surface topography analysis should be easy to implement to any phase change material exhibiting sizeable electron-lattice coupling. In addition, AFM images revealed specific topographic features in the crystals, which were correlated with the spatiotemporal evolution of the transition observed by far-field and near-field optical microscopies. We imaged a spin transition through both the electronic and lattice degrees of freedom using variable temperature scanning probe microscopy.